<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<style>
    .outer {
        width: 100%;
        height: 100px;
    }
    .left {
        width: 100px;
        height: 100px;
        float: left;
        background-color: #bbffaa;
    }
    .right {
        float: left;
        height: 100px;
        width: calc(100% - 100px);
        background-color: red;
    }
</style>
<body>
<div class="outer">
    <!--左边固定 右边自适应-->
    <div class="left"></div>
    <div class="right"></div>
</div>
</body>
</html>
